Servlet note three

One: connection pool

1. Concept: Create quantitative connection objects for web applications, save them in memory (connection pool), obtain connection objects from the pool each time you access, and put them back into the pool after use.

2. Tomcat connection pool development process: //The password cannot be too short

I. Provide the database connection Jar package (ojdbc5.jar) and import it into tomcat/lib.

"ojdbc5.jar" for jdk5.0.

"ojdbc6.jar", for jdk6.0.

"ojdbc14.jar" for JDK 1.4 and 5.0.

Note: If the jdk version is high, you can use "ojdbc6.jar".

II. Add the <resource /> tag in tomcat/conf/context.xml.

III. Encoding: // 1. Get Context.xml object 2. Find access name

//java:comp/env/ is a fixed way of writing JNDI in java.

IV. Note: It belongs to Tomcat and must be used in the web environment. The main function junit test cannot be used.

V. Disadvantages: The coupling with the server is too strong, which is not conducive to maintenance. It is recommended to use third-party open source connection pools and framework connection pools (MyBatis, Hibernate, Spring).

3. DBCP connection pool usage process: third-party connection pool

I. Import the Jar package (ojdbc6.jar)

II. Import configuration files. (The key cannot be changed---the value can be changed)

III. Coding:

Two: filter

1. Concept:

I. The javax.servlet.Filter interface is an implementation class object, an object created when the server starts.

II. The execution status is before the Servlet. When requesting, it will go through the Filter first and then reach the target Servlet; when responding, the Filter will be executed in reverse again according to the execution process.

III. It can solve the redundant problem of common codes of multiple servlets (garbled code processing, login verification).

2. Implementation steps:

①: Customize the implementation of the Filter interface

②: Rewrite the three methods in javax.servlet.Filter

init initialization, called when the program loads

The end of the destruction web program

doFilter() 核心拦截办法

	public class MyFilter implements Filter {
	@Override
	public void destroy() {

	}
	// 核心拦截方法
	@Override
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
			throws IOException, ServletException {
		request.setCharacterEncoding("UTF-8");
		response.setContentType("text/html;charset=UTF-8");
		// 允许链继续调用下一个Filter，若无过滤器，则负责传递到Servlet
		chain.doFilter(request, response);
	}
	@Override
	public void init(FilterConfig filterConfig) throws ServletException {

	}
}